Baby boomers and birth certificates: Early-life socioeconomic status and cancer risk in adulthood

Background: Early-life socioeconomic status (SES) may play a role in cancer risk in adulthood. However, measuring SES retrospectively presents challenges. Parental occupation on the birth certificate is a novel method of ascertaining early-life SES that has not been applied in cancer epidemiology. Methods: For a Baby-Boom cohort born from 1945-1959 in two Utah counties, individual-level Nam-Powers SES (Np-SES) was derived from parental industry/occupation reported on birth certificates. Neighborhood SES was estimated from average household income of census tract at birth. Cancer incidence was determined by linkage to Utah Cancer Registry records through the Utah Population Database. Hazard ratios (HR) for cancer risk by SES quartile were estimated using Cox proportional hazards regression. Results: Females with low Np-SES at birth had lower risk of breast cancer compared with those in the highest Np-SES group [HR_Q1/Q4 =0.83; 95% confidence interval (CI), 0.72-0.97; HR_Q2/Q4 =0.81; 95% CI, 0.69-0.96]. Np-SES was inversely associated with melanoma (HR_Q1/Q4 =0.81; 95% CI, 0.67- 0.98) and prostate cancer (HR_Q1/Q4 =0.70; 95% CI, 0.56- 0.88). Women born into lower SES neighborhoods had significantly increased risk for invasive cervical cancer (HR_Q1/Q4 =1.44; 95% CI, 1.12-1.85; HR_Q2/Q4 =1.33; 95% CI, 1.04-1.72). Neighborhood SES had similar effects for melanoma and prostate cancers, but was not associated with female breast cancer. We found no association with SES for pancreas, lung, and colon and rectal cancers. Conclusions: Individual SES derived from parental occupation at birth was associated with altered risk for several cancer sites. Impact: This novel methodology can contribute to improved understanding of the role of early-life SES on cancer risk.